Integrated catalytic cracking with ethanol conversion to fuel

ABSTRACT

Processes relating to the conversion of ethanol in a stripper unit of a fluidized catalytic cracking system. An ethanol stream comprising at least 4 volume percent water mixes with a catalyst in the stripper unit under conditions of temperature that favor conversion of the ethanol to hydrocarbons, thereby increasing incorporation of ethanol into liquid transportation fuels without exceeding regulatory limits on fuel vapor pressure. Certain embodiments additionally combine the ethanol stream with a hydrocarbon stream in the stripper and react in the presence of a catalyst to produce hydrocarbons that may have an increased boiling point, increased octane rating, decreased vapor pressure, decreased benzene content, or combinations of these properties.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This application is a non-provisional application which claims thebenefit of and priority to U.S. Provisional Application Ser. No.62/096,916 filed Dec. 26, 2014, titled “Integrated Catalytic Crackingwith Ethanol Conversion to Fuel,” which is hereby incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

US government mandates have required increasing quantities ofbiomass-derived ethanol to be blended into transportation fuels. Due toconcurrent reductions in US gasoline production and consumption, thequantity of ethanol blended into gasoline may soon exceed 10%, which mayhave implications for the operability of certain older vehicles notdesigned to utilize such fuels. Additionally, blending of increasingquantities of biomass-derived ethanol into fuels can increase theoverall Reid vapor pressure to levels that exceed government mandatedlevels.

Thus, a need exists for new methods and systems that allow increasedincorporation of biomass-derived ethanol into liquid transportationfuels, while preserving the suitability of the resulting fuel for use inmost vehicles and maintaining an acceptable Reid vapor pressure of thefuel.

BRIEF SUMMARY OF THE DISCLOSURE

Certain embodiments of the inventive process comprise converting ethanolto liquid transportation fuels by mixing and reacting a catalyst with anethanol stream and a hydrocarbon stream within a conversion unit toproduce a mixed product stream comprising hydrocarbons having anincreased average molecular weight. The hydrocarbons are conveyed to afluidized catalytic cracking unit (FCCU). The catalyst is preferablyutilized to replenish the catalyst within the fluidized catalyticcracking unit.

Optionally, the ethanol stream comprises water that is converted tosteam either prior to, or upon entering the conversion unit to preventcontact between the liquid water and the catalyst. In certainembodiments, the ethanol stream is derived from biomass and comprises atleast 4 weight percent of water.

In certain embodiments of the inventive process, the reacting comprisesalkylation, oligomerization, condensation or combinations thereof. Incertain embodiments, the reacting may decreases the Reid vapor pressure,the total benzene content, or both, of the mixed product stream. Incertain embodiments, the reacting increases at least one of themolecular weight, the alkylaromatics content and the octane rating ofthe mixed product stream.

In certain embodiments the hydrocarbon stream comprises at least one ofcracked hydrocarbons, light olefins or benzene. In certain embodiments,the hydrocarbon stream comprises cracked hydrocarbons produced by thefluidized catalytic cracking unit. In certain embodiments, thehydrocarbon stream is a fraction obtained from a fractionator locatedimmediately downstream from the fluidized catalytic cracking unit.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention and benefitsthereof may be acquired by referring to the follow description taken inconjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram depicting one embodiment of a system andprocess for converting ethanol to liquid fuels in a conversion reactorlocated upstream from a fluidized catalytic cracking unit (FCCU).

The invention is susceptible to various modifications and alternativeforms, specific embodiments thereof are shown by way of example in thedrawings. The drawings may not be to scale. The drawing and itsaccompanying detailed description are not intended to limit the scope ofthe invention to the specific embodiment. The present disclosure isintended to cover all modifications, equivalents and alternativesfalling within the spirit and scope of the present invention as definedby the appended claims.

DETAILED DESCRIPTION

Various exemplary embodiments of the inventive processes and systemswill now be described in more detail. Certain embodiments pertain to theconversion of biomass-derived ethanol to transportation fuels in aconversion unit located upstream from an FCCU. Certain embodimentsadditionally pertain to co-converting a mixture comprising an ethanolstream and a hydrocarbon stream, where the hydrocarbon stream isoptionally cracked hydrocarbons produced in a Fluidized CatalyticCracking (FCC) riser, a highly-aromatic hydrocarbon fraction obtainedfrom a fractionator that separates hydrocarbons cracked in the FCCU, orcombinations thereof. The inventive processes and systems effectivelyallow incorporation of greater quantities of biomass-derived ethanolinto liquid transportation fuels without raising the final ethanolcontent of the finished fuel above about 10 weight percent, and withoutincreasing the Reid vapor pressure of the finished fuel to levels deemedunacceptable by government regulations.

FIG. 1 details components of an exemplary process and system. Aconversion unit 20 comprising an internal reaction zone 25 accepts andfacilitates contact between an ethanol stream 30 and a fresh catalyst 40to facilitate conversion of the ethanol stream 30 by the catalyst 40 toa mixed product stream 50 comprising hydrocarbons that is conveyed tothe reactor (or separation vessel) 130 of an FCCU. The now spentcatalyst 60 is either returned directly to the regenerator 160, or maybe conveyed along with the mixed product stream 50 to reactor 130, whereit is separated from the mixed product stream 50 by cyclones 120 andeventually regenerated in the regenerator 160.

In the embodiment depicted in FIG. 1, the conversion unit 20additionally receives a hydrocarbon stream 80 that mixes with the freshcatalyst 40 and the ethanol stream 30 in the reaction zone and isconverted along with the ethanol stream 30 to produce the mixed productstream.

The general operation of an FCCU is well-understood in the art and willonly be described herein to a level of detail that helps illustrate theimprovements provided by the inventive systems and processes describedherein. FCC is characterized by the use of a finely-dividedsilica/alumina based catalyst that is moved through the FCCU. Acommercial-scale FCCU is a large-scale process and unit throughputs aretypically in the range of about 10,000 to 130,000 barrels per day, whichcorresponds to catalyst circulation rates of 7 to 130 tons per minute.The catalyst particles typically utilized are of such a size that when“fluidized” with air or hydrocarbon vapor, the catalyst particles behavelike a liquid and can be transported through pipes.

Again referring to FIG. 1, in the FCCU a petroleum-derived feedstock 50and a regenerated catalyst 70 flow into a vertically-oriented riser 100comprising a reaction zone where a majority of initial crackingreactions take place. The petroleum-derived feedstock 50 and thecatalyst 70 mix and rise through the riser 100 as the petroleum-derivedfeedstock 50 is vaporized and cracked. Cracked vapors and the catalyst(which is now spent) leave via an outlet that is located proximate theupper portion of the riser 100, and are then separated as they passthrough cyclones 120 located just downstream from the riser 100 in thereactor (or separation vessel) 130, which separates spent catalyst fromthe cracked vapors.

In the embodiment depicted in the Figure, the cracked vapors mix withthe mixed product stream 50 coming from the conversion unit 25 toproduce a second mixed product stream 140 that passes out of the reactor130. The second mixed product stream 140 is then directed to enter oneor more fractionating towers (not depicted), which fractionate thecracked vapors into light and heavy-cracked gas oils, cracked gasoline,and non-condensable, C1-C3 gases. Certain hydrocarbon fractionsseparated by the fractionator (not depicted) may possess a relativelyhigh level of benzene that is unsuitable for blending intotransportation fuels due to environmental regulations. Such hydrocarbonfractions may be suitable for feeding to the conversion unit 20 ashydrocarbon stream 80.

The ethanol stream 30 is optionally derived from biomass, in which caseit may be produced from biomass via any known mechanism (such as, butnot limited to, fermentation). Such production methods are conventionaland outside the scope of the invention. In certain embodiments, theethanol stream is a raw ethanol stream comprising at least 4 volumepercent water. A raw ethanol stream is defined herein as an ethanolstream derived from biomass that comprises at least 4 volume percent ofwater.

In certain embodiments, prior to addition to the conversion unit, thefresh catalyst 40 is adjusted to a temperature that assists in alteringthe temperature within the conversion unit. For example, in oneembodiment the temperature of the fresh catalyst may be lower than thetemperature within the conversion unit, which causes quenching, orlowering of the temperature within the conversion unit. Quenching theconversion unit to a lower temperature may assist in optimizing thetemperature to facilitate certain chemical reactions within the stripperunit. Alternatively, the fresh catalyst may be adjusted to a temperaturethat is higher than the temperature that is maintained within theconversion unit in order to help supply at least part of the heatrequired for a given conversion reaction.

Again referring to FIG. 1, the conversion unit 20 additionally comprisesat least one inlet for the entry of fresh catalyst 40. The freshcatalyst serves to catalyze conversion of ethanol stream (and optionallya hydrocarbon stream 80) in the conversion unit to a mixed productstream that predominantly comprises hydrocarbons containing 4-15 carbonatoms and spent catalyst. The mixed product stream is then conveyed fromthe conversion unit along with spent catalyst to the reactor (orseparation unit) 130 where it is separated from the spent catalyst bycyclones 120 or other conventional mechanisms that are outside the scopeof the invention. The mixed product stream 60 is maintained in vaporphase and directed to a downstream fractionator (not depicted), whichfractionates the cracked vapors by boiling point into light andheavy-cracked gas oils, cracked gasoline, jet fuel and dieselblendstock, C₃-C₄ products (sometimes called liquefied petroleum gasses,or LPG), and non-condensable gases including, but not limited to, H₂,H₂S, methane, and C₂ gases. Such fractionation methods are conventionaland are outside the scope of the invention, and will not be discussedfurther.

In certain alternative embodiments, the hydrocarbon stream that isco-fed to the conversion unit along with the ethanol stream may be afraction re-directed from the downstream fractionator that separates themixed product stream (and cracked hydrocarbons produced by the FCCU)into various fractions according to their boiling point. The hydrocarbonstream advantageously comprises a fraction that comprises a largepercentage of aromatic compounds. In these embodiments, the aromaticcompounds are at least partially converted in the conversion unit tohydrocarbons that may possess an increased molecular weight, anincreased boiling point, a decreased Reid vapor pressure, an increasedoctane rating, or combinations of more than one of these attributes.

While not wishing to be bound by theory, embodiments that mix ahydrocarbon stream and an ethanol stream together with a catalyst in astripper unit may provide an advantage by facilitating increasedchemical reactions between the hydrocarbon stream and the ethanol in theethanol stream. In certain embodiments, this may serve to facilitate theconversion of benzene in the hydrocarbon stream to alkylaromatics,thereby decreasing the quantity of benzene in the mixed product stream.In certain embodiments, this conversion may facilitate an increase theoctane rating of the mixed product stream comprising hydrocarbons, ordecrease the Reid vapor pressure of the mixed product stream, orcombinations of these effects.

The conversion unit is optionally maintained in a temperature range thatis optimized to favor certain chemical reactions, such as (but notlimited to) oligomerization, condensation and alkylation. For example, aconversion unit receiving only a feed of raw ethanol stream may betemperature-optimized for the catalyzed conversion of ethanol to C4-C15hydrocarbons. Alternatively, a conversion unit may optionally bemaintained within a temperature range to favor the alkylation ofaromatics by ethanol. Alternatively, a conversion unit may be maintainedwithin a temperature range to favor the reaction between olefins andethanol to form C4-C15 hydrocarbons.

To accomplish these goals, the conversion unit may be maintained at atemperature ranging from 260° C. (500° F.) to 550° C. (1022° F.),optionally 315° C. (600° F.) to 510° C. (950° F.), optionally 650° F. to950° F., optionally 550° F. to 800° F. 700° F. to 950° F., optionally750° F. to 900° F., optionally 700° F. to 850° F., optionally 700° F. to900° F., optionally 800° F. to 900° F., optionally 700° F. to 800° F.and a pressure ranging from about 1 to 145 psig (0.07 to 10 bar).

Referring again to FIG. 1, once the spent catalyst has been transportedfrom the conversion unit to the FCC reactor 130, it is steam-stripped toremove hydrocarbons in the stripper unit 150, and eventually istransported to a regenerator 160, where coke is removed from thecatalyst by controlled combustion in a conventional manner that isoutside the scope of the invention. Regenerated catalyst 70 then entersthe riser 100 via an inlet proximate the bottom portion of the riser 100and in close proximity to the inlet for the petroleum-derived FCCfeedstock 50. This allows the regenerated catalyst 70 to assist invaporizing the fresh petroleum-derived FCC feedstock 50 just prior tocracking of the feedstock in the riser 100.

Optionally, the ethanol stream may comprise from 4 to 95 volume percentwater, inclusive. In certain embodiments, the ethanol stream maycomprise up to 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, or even as much as95 volume percent water, inclusive, without adversely affectingconversion of the ethanol stream to hydrocarbons by the catalyst(depending upon the sensitivity of the catalyst utilized to deactivationby water vapor). In certain embodiments, the wt. % of water in theethanol stream may find an upper limit, although this upper limit mayvary significantly depending upon the catalyst utilized and theconditions of temperature and pressure in each stripper unit.

In general, the temperature within the conversion unit is sufficient toprevent condensation of water that is present, including water that isfed to the stripper unit as a component of the raw ethanol stream. Thisprevents damage to the catalyst within the stripper unit, particularlyif the catalyst comprises one or more metals. Alternatively, a certainquantity of water may be removed from the raw ethanol stream to producea partially-processed ethanol stream prior to entering the stripperunit. Techniques for achieving this separation may include distillation,pervaporation (such as in the presence of a zeolite membrane) or anyother conventional separation methodology.

The catalyst used in the conversion unit for any embodiment may compriseany catalyst that is capable of facilitating the cracking of largehydrocarbons into smaller hydrocarbons at a suitable temperature, whileadditionally capable of catalyzing the conversion of ethanol and/orhydrocarbons to produce larger hydrocarbons comprising four or morehydrocarbons. The catalyst is preferably resistant to the presence ofwater.

In certain embodiments, the catalyst may comprise any type of zeolitethat is capable of catalyzing reactions between hydrocarbons to producea higher molecular weight hydrocarbon. Such zeolites may be, but are notlimited to, zeolites of one or more of the following categories: Y, X,MFI, FAU, beta, HY, EMT, USY, MOR, LTL BEA, MCM, ZSM, REY, REUSY andSAPO. The catalyst may also be impregnated with a metal, such as, forexample, a rare earth metal, alkali metal, or alkaline earth metal. Incertain embodiments, the aluminum of the zeolite structure can betotally or partially substituted by poor metals such as, for example, B,Ga, or Fe. An extensive characterization of such catalysts andstructural or substituted variants is well known in the art.

The following examples are provided to better illustrate one or more ofthe various embodiments.

EXAMPLE 1

Table 1 shows the selectivity of the ethanol conversion reaction towardsproduction of C5+ hydrocarbons. A feed mixture comprising ethanol wasfed at 2 g/hr (per 5 g catalyst) in the presence of a gaseous mix ofH₂/N₂/H₂O (ratio of 36/23/8 by volume). A zeolite catalyst ZSM-5 wascontacted with the mixture at a temperature of 320° C. and 50 psig. Theresults (depicted in Table 1) demonstrated that production ofhydrocarbons comprising five or more carbons (C5+) was highly-favored.

TABLE 1 Product Selectivity from the Conversion of Ethanol toHydrocarbons Ethanol Conversion (wt. %) ~100 Product Selectivity (wt. %)Methane 0.0 Ethane 0.5 Propane 3.7 Propylene 1.3 Butanes 14.3 Butenes2.9 C5+ 77.2 Total, (wt. %) ~100.0

EXAMPLE 2

Table 2 provides an example of co-conversion between ethanol and theolefin ethylene, demonstrating the feasibility of embodiments where bothan ethanol stream and a stream of hydrocarbons are fed to a conversionunit containing a zeolite catalyst. The table shows the product profileresulting from the co-conversion of the olefin ethylene (one example ofa hydrocarbon produced in an FCC riser) and ethanol over a zeolitecatalyst. A first feed comprised a mixture of ethylene/H₂/N₂/H₂O (ratioof 33/36/23/8 by volume) fed with an ethylene weight hour space velocity(WHSV) of 1.0 hr⁻¹. A second feed was ethanol fed at 2 g/hr (per 5 gcatalyst). The zeolite catalyst ZSM-5 was contacted with the mixtureunder the following conditions: 310° C., 0 psig, 1.0 hr⁻¹ (EthyleneWHSV), H₂/N₂/Ethylene/H₂O.

TABLE 2 Product Selectivity from the Co-conversion of Ethylene andEthanol to Hydrocarbons Ethylene Conversion (wt. %) 86.5 EthanolConversion (wt. %) ~100 Product Selectivity (wt. %) Methane 0.0 Ethane0.4 Propane 2.4 Propylene 5.3 Butanes 11.3 Butenes 11.2 C5+ Products69.4 Total (wt %) 100.0

An advantage of the present processes and systems is that the freshcatalyst is added to the system via the conversion unit and is thentransported from the conversion unit to the downstream fluidizedcatalytic cracking unit, wherein can serve to replenish old crackingcatalyst. The conversion unit can be maintained at a temperature thatfavors reactions that upgrade the ethanol stream (optionally, a mixtureof an ethanol stream and a hydrocarbon stream) to hydrocarbonscomprising five or more carbon atoms that can be blended intotransportation fuels.

An additional advantage of the inventive systems and processes disclosedherein is to avoid the need to separate water from the ethanol streamprior to feeding this stream to the conversion unit, as this wouldincrease costs and reduce commercial viability of the system andprocess.

Although the systems and processes described herein have been describedin detail, it should be understood that various changes, substitutions,and alterations can be made without departing from the spirit and scopeof the invention as defined by the following claims. Those skilled inthe art may be able to study the preferred embodiments and identifyother ways to practice the invention that are not exactly as describedherein. It is the intent of the inventors that variations andequivalents of the invention are within the scope of the claims whilethe description, abstract and drawings are not to be used to limit thescope of the invention. The invention is specifically intended to be asbroad as the claims below and their equivalents.

We claim:
 1. A process for converting ethanol to liquid transportationfuels, the process comprising mixing and reacting a catalyst with anethanol stream and a hydrocarbon stream within a conversion unit toproduce a mixed product stream comprising hydrocarbons having anincreased average molecular weight, wherein the mixed product stream isnext conveyed to a fluidized catalytic cracking unit.
 2. The processaccording to claim 1, wherein the hydrocarbon stream comprises at leastone of cracked hydrocarbons, light olefins or benzene.
 3. The processaccording to claim 1, wherein the reacting comprises alkylation,oligomerization, condensation or combinations thereof.
 4. The processaccording to claim 1, wherein the reacting decreases the Reid vaporpressure, the total benzene content, or both, of the mixed productstream.
 5. The process according to claim 1, wherein the reactingincreases at least one of the molecular weight, the alkylaromaticscontent and the octane of the mixed product stream.
 6. The processaccording to claim 1, wherein the catalyst is used to replenish thecatalyst within the fluidized catalytic cracking unit.
 7. The processaccording to claim 1, wherein the ethanol stream is derived from biomassand comprises at least 4 weight percent of water.
 8. The processaccording to claim 6, wherein the water in the ethanol stream isconverted to steam either prior to, or upon entering the conversion unitto prevent contact between the liquid water and the catalyst.
 9. Theprocess according to claim 1, wherein the hydrocarbon stream comprisescracked hydrocarbons produced by the fluidized catalytic cracking unit.10. The process according to claim 1, wherein the hydrocarbon stream isa fraction obtained from a fractionator located immediately downstreamfrom the fluidized catalytic cracking unit.